In the field of existing curved display devices, the upper glass substrate is bonded to the lower glass substrate by means of a sealant. Upon being curved, the upper glass substrate 12 (in the case of operating the curved display device, the upper glass substrate 12 is closer to the viewer) always bears a compressive stress, as shown in FIG. 1, and the lower glass substrate 16 (in the case of operating the curved display device, the lower glass substrate 16 is usually far from the viewer) always bears a tensile stress, as shown in FIG. 2. This is because the lower glass substrate 16 encloses the external side of the upper glass substrate 12, which limits recovery of the elasticity of the upper glass substrate 12 to its original state. As can be seen from the middle area 13, the upper-left corner area 14a and the upper-right corner area 14b as shown in FIG. 1, the stresses in the areas close to the middle area 13 of the upper glass substrate 12 substantially exhibit a horizontal state. It can be regarded that the compressive stresses they bear are at a level close to 0° or 180°. In other words, the optical axes in the middle area 13 of the upper glass substrate 12 are close to 0° or 180°. The stresses in the areas close to the edges such as corners, for example, the upper-left corner area 14a and the upper-right corner area 14b, substantially exhibit an inclined state, and the closer the areas are to the corners, the larger the inclined angles of the stresses become. It can be regarded that the compressive stresses they bear are at a level close to 30° or −30°, and for the areas closer to the corner areas of the upper glass substrate 12, i.e. four corner areas, the compressive stresses they bear are even at a level close to 45° or −45°. In other words, the optical axes in the upper-left corner area 14a and the upper-right corner area 14b of the upper glass substrate 12 are close to 30° or −30°, and in the areas closer to the corner areas of the upper glass substrate 12, the optical axes are at a level closer to 45° or −45°, which is usually considered in the art as the maximum light leaking angle.
Likewise, as can be seen from the middle area 17, the upper-left corner area 18a and the upper-right corner area 18b of the lower glass substrate 16 as shown in FIG. 2, the stresses in the areas close to the middle area 17 of the lower glass substrate 16 substantially exhibit a horizontal state. It can be regarded that the tensile stresses they bear or the optical axes in the middle area 17 are close to 0° or 180°. The tensile stresses in the areas close to the corners, for example, the upper-left corner area 18a and the upper-right corner area 18b, substantially exhibit an inclined state. It can be regarded that the tensile stresses they bear are at a level close to 30° or −30°, and in the areas closer to the corner areas of the lower glass substrate 16, i.e. four corner areas, the tensile stresses they bear are even at a level close to 45° or −45°. In other words, the optical axes in the upper-left corner area 18a and the upper-right corner area 18b are close to 30° or −30°, even close to 45° or −45°.
Furthermore, in the existing curved display devices, surfaces of the upper glass substrate 12 and the lower glass substrate 16 are usually further provided with polarizers whose polarization directions are orthogonal to each other, so as to prevent transmission of light in dark state. However, for the existing curved display devices, there is a lot of light leakage at four corners of each of the upper glass substrate 12 and lower glass substrate 16, and the function of blocking transmission of light in dark state cannot be well achieved. That is, there is considerable light leakage.
Therefore, for the existing curved display devices, there is an urgent demand for improving the above problems.